Select Works, Section 373 (part 1)

Section 7 7. Our investigation may be furthered by enquiring: Whether light finally perishes or simply returns to its source. If it be a thing requiring to be caught and kept, domiciled within a recipient, we might think of it finally passing out of existence: if it be an Act not flowing out and away- but in circuit, with more of it within than is in outward progress from the luminary of which it is the Act- then it will not cease to exist as long as that centre is in being. And as the luminary moves, the light will reach new points- not in virtue of any change of course in or out or around, but simply because the act of the luminary exists and where there is no impediment is effective. Even if the distance of the sun from us were far greater than it is, the light would be continuous all that further way, as long as nothing checked or blocked it in the interval. We distinguish two forms of activity; one is gathered within the luminary and is comparable to the life of the shining body; this is the vaster and is, as it were, the foundation or wellspring of all the act; the other lies next to the surface, the outer image of the inner content, a secondary activity though inseparable from the former. For every existent has an Act which is in its likeness: as long as the one exists, so does the other; yet while the original is stationary the activity reaches forth, in some things over a wide range, in others less far. There are weak and faint activities, and there are some, even, that do not appear; but there are also things whose activities are great and far-going; in the case of these the activity must be thought of as being lodged, both in the active and powerful source and in the point at which it settles. This may be observed in the case of an animal's eyes where the pupils gleam: they have a light which shows outside the orbs. Again there are living things which have an inner fire that in darkness shines out when they expand themselves and ceases to ray outward when they contract: the fire has not perished; it is a mere matter of it being rayed out or not. But has the light gone inward? No: it is simply no longer on the outside because the fire [of which it is the activity] is no longer outward going but has withdrawn towards the centre. But surely the light has gone inward too? No: only the fire, and when that goes inward the surface consists only of the non-luminous body; the fire can no longer act towards the outer. The light, then, raying from bodies is an outgoing activity of a luminous body; the light within luminous bodies- understand; such as are primarily luminous- is the essential being embraced under the idea of that body. When such a body is brought into association with Matter, its activity produces colour: when there is no such association, it does not give colour- it gives merely an incipient on which colour might be formed- for it belongs to another being [primal light] with which it retains its link, unable to desert from it, or from its [inner] activity. And light is incorporeal even when it is the light of a body; there is therefore no question, strictly speaking, of its withdrawal or of its being present- these terms do not apply to its modes- and its essential existence is to be an activity.